Modern communications systems may permit access to a service through multiple devices acting as user endpoints. For example, a user may initially access a voice over long term evolution (VoLTE) service using a smartphone acting as a primary endpoint. As a convenience to facilitate access to the service, the user may add a secondary endpoint (e.g., a tablet) associated with the phone number of the smartphone for the VoLTE service. Once added, the tablet, acting as the secondary endpoint, may send and/or receive VoLTE calls using the phone number of the smartphone. In conventional systems, designating the secondary endpoint for a service may involve having the user manually enter one or more network identifiers (e.g., the phone number) of the primary endpoint and/or validating credentials into the device that the user wishes to designate as the secondary endpoint.